1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel that is capable of improving discharge efficiency.
2. Description of the Related Art
Generally, a plasma display panel (PDP) is a display device utilizing a visible light emitted from a fluorescent layer when an ultraviolet ray generated by a gas discharge excites the fluorescent layer. The PDP has an advantage in that it has a thinner thickness and a lighter weight in comparison to the existent cathode ray tube (CRT) and is capable of realizing a high resolution and a large-scale screen. The PDP includes a plurality of discharge cells arranged in a matrix pattern, each of which makes one pixel of a field.
FIG. 1 is a perspective view showing a discharge cell structure of a conventional three-electrode, alternating current (AC) surface-discharge PDP.
Referring to FIG. 1, a discharge cell of the conventional three-electrode, AC surface-discharge PDP includes a scanning/sustaining electrode 12Y and a common sustaining electrode 12Z provided on an upper substrate 10, and an address electrode 20X provided on a lower substrate 18.
On the upper substrate 10 provided with the scanning/sustaining electrode 12Y and the common sustaining electrode 12Z in parallel, an upper dielectric layer 14 and a protective film 16 are disposed. Wall charges generated upon plasma discharge are accumulated into the upper dielectric layer 14. The protective film 16 prevents a damage of the upper dielectric layer 14 caused by a sputtering during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 16 is usually made from magnesium oxide (MgO).
A lower dielectric layer 22, barrier ribs 24 are formed on the lower substrate 18 provided with the address electrode 20X. The surfaces of the lower dielectric layer 22 and the barrier ribs 24 are coated with a fluorescent layer 26. The address electrode 20X is formed in a direction crossing the scanning/sustaining electrode 12Y and the common sustaining electrode 12Z.
The barrier rib 24 is formed in parallel to the address electrode 20X to prevent an ultraviolet ray and a visible light generated by a discharge from being leaked to the adjacent discharge cells. The fluorescent layer 26 is excited by an ultraviolet ray generated during the plasma discharge to generate any one of red, green and blue visible light rays. An inactive gas for a gas discharge is injected into a discharge space defined between the upper and lower substrate 10 and 18 and the barrier rib 24.
Such a three-electrode AC surface-discharge PDP drives one frame, which is divided into various sub-fields having a different discharge number, so as to realize gray levels of a picture. Each sub-field is again divided into a reset period for uniformly causing a discharge, an address period for selecting the discharge cell and a sustaining period for realizing the gray levels depending on the discharge number.
For instance, when it is intended to display a picture of 256 gray levels, a frame interval equal to {fraction (1/60)} second (i.e. 16.67 msec) is divided into 8 sub-fields. Each of the 8 sub-fields is again divided into a reset period, an address period and a sustaining period. The reset period and the address period of each sub-field are equal every sub-field, whereas the sustaining period thereof is increased at a ration of 2n (wherein n=0, 1, 2, 3, 4, 5, 6 and 7) at each sub-field. Since the sustaining period becomes different at each sub-field as mentioned above, the gray levels of a picture can be expressed.
In the reset period, a reset pulse is applied to the scanning/sustaining electrode 12Y to cause a reset discharge. In the address period, a scanning pulse is applied to the scanning/sustaining electrode 12Y and a data pulse is applied to the address electrode 20X, to thereby cause an address discharge between two electrodes 12Y and 20X. During the address discharge, wall charges are formed on the upper and lower dielectric layers 14 and 22. In the sustaining period, a sustaining discharge is caused between two electrodes 12Y and 12Z by an alternating current signal alternately applied to the scanning/sustaining electrode 12Y and the common sustaining electrode 12Z.
However, the conventional AC surface-discharge PDP has a sustaining discharge space concentrated at the center of the upper substrate 10 to reduce a utility of the discharge space. Thus, it has a problem that the reduced discharge area deteriorate a light emission efficiency.
In order to solve this problem, there has been suggested a five-electrode, AC surface-discharge PDP as shown in FIG. 2.
Referring to FIG. 2, the conventional five-electrode, AC surface-discharge PDP includes first and second trigger electrodes 34Y and 34Z provided on an upper substrate 30 in such a manner to be positioned at the center of a discharge cell, first and second sustaining electrodes 32Y and 32Z provided on the upper substrate 30 in such a manner to be positioned at the edge of the discharge cell, and an address electrode 42X provided at a lower substrate in a direction crossing the trigger electrodes 34Y and 34Z and the first and second sustaining electrodes 32Y and 32Z.
On the upper substrate 30 provided with the first sustaining electrode 32Y, the first trigger electrode 34Y, the second trigger electrode 34Z and the second sustaining electrode 32Z in parallel, an upper dielectric layer 36 and a protective layer 38 are disposed. On the other hand, a lower dielectric layer 44 and a barrier rib 46 are formed on a lower substrate 40 provided with the address electrode 42X, and a fluorescent layer 48 is coated on the surfaces of the lower dielectric layer 44 and the barrier ribs 46.
The trigger electrodes 34Y and 34Z spaced at a narrow distance Ni at the center of the discharge cell are supplied with a sustaining pulse in the sustaining period to initiate a sustaining discharge. The first and second sustaining electrodes 32Y and 32Z spaced at a wide distance Wi at the edge of the discharge cell maintain a plasma discharge after the discharge between the trigger electrodes 34Y and 34Z was initiated by an application of a sustaining pulse in the sustaining period.
FIG. 3 is a section view representing a state of rotating the upper substrate by 90xc2x0 with respect to the lower substrate so as to show up the overall electrode structure within one discharge cell.
An operation process of the five-electrode AC surface-discharge PDP will be described in detail with reference to FIG. 3 and FIG. 4 below.
The five-electrode AC surface-discharge PDP drives one frame, which is divided into various sub-fields having a different discharge number, so as to realize gray levels of a picture. Each sub-field is again divided into a reset period for uniformly causing a discharge, an address period for selecting the discharge cell and a sustaining period for expressing the gray levels depending on the discharge number.
First, in the reset period, a reset pulse is applied to the second trigger electrode Tz of the discharge cell to generate a reset discharge for initializing the discharge cell. At this time, the address electrode X is supplied with a direct current voltage for preventing an erroneous discharge.
In the address period, a scanning pulse C is sequentially applied to the first trigger electrode Ty and a data pulse Va synchronized with the scanning pulse C is applied to the address electrode X. At this time, an address discharge is generated at the discharge cells supplied with the data pulse Va.
In the sustaining period, a sustaining pulse is alternately applied to the first trigger electrode Ty and a first sustaining electrode Sy and the second trigger electrode Tz and a second sustaining electrode Sz. In this case, a voltage Vt applied to the trigger electrodes Ty and Tz has a lower level than a voltage Vs applied to the first and second sustaining electrodes Sy and Sz.
When such a sustaining pulse is applied, a primary discharge is caused between the first and second trigger electrodes Ty and Tz. In other words, a primary discharge is generated between the first and second trigger electrodes Ty and Tz, and a secondary discharge is induced between the first and second sustaining electrodes Sy and Sz with the aid of a priming effect of charged particles generated by the primary discharge.
The sustaining pulse applied to the sustaining period may be alternately applied between the first trigger electrode Ty and the second sustaining electrode Sz and the second trigger electrode Tz and the first sustaining electrode Sy as shown in FIG. 5. If the primary discharge is generated between the trigger electrodes Ty and Tz as mentioned above, then a sustaining discharge can be generated due to a priming discharge between the trigger electrodes Ty and
Tz even though a distance Wi between the first sustaining electrode Sy and the second sustaining electrode Sz is large. In other words, electrons emitted from the first and second sustaining electrodes Sy and Sz have a long path. If electrons have a long path, then a quantity of ultraviolet rays generated by a collision of electrons with an inactive gas is increased, and thus the increased ultraviolet rays excite a fluorescent material 48 to create a lot of visible lights from the fluorescent material 48.
However, the scanning pulse C is applied only to the first trigger electrode Ty in the address period in the conventional five-electrode PDP. Thus, wall charges produced by the address discharge are formed only at the first trigger electrode Ty. In other words, since wall charges are formed only at the first trigger electrode Ty, the sustaining discharge occurring between the first and second sustaining electrodes Sy and Sz fails to utilize the wall charges produced in the address period.
Accordingly, in order to cause an effective sustaining discharge, a sustaining pulse having a high voltage level should be applied to the first and second sustaining electrodes Sy and Sz. However, if a sustaining pulse having a high voltage level is applied to the first and second sustaining electrodes Sy and Sz, then an erroneous discharge occurs with respect to the address electrode X.
In the mean time, the primary discharge between the trigger electrodes Ty and Tz for initiating a sustaining discharge should be a minute discharge. However, a strong discharge occurs between the trigger electrodes Ty and Tz spaced at a narrow distance Ni. If a strong discharge is generated between the trigger electrodes Ty and Tz, then a sustaining discharge between the first sustaining electrode Sy and the second sustaining electrode Sz occurs weakly.
If a weak discharge occurs between the first and second sustaining electrodes Sy and Sz, then a quantity of ultraviolet rays exciting the fluorescent material is reduced to deteriorate discharge efficiency. Furthermore, wall charges formed by the primary discharge between the trigger electrodes Ty and Tz get lost due to the sustaining discharge of the first and second sustaining electrodes Sy and Sz. If wall charges formed at the rear sides of the trigger electrodes Ty and Tz get lost, then a high voltage should be applied so as to cause a primary discharge between the trigger electrodes Ty and Tz.
Accordingly, it is an object of the present invention to provide a plasma display panel that is adaptive for improving discharge efficiency.
In order to achieve these and other objects of the invention, a plasma display panel according to an embodiment of the present invention includes trigger electrodes provided at the center of an upper substrate; sustaining electrodes provided at the upper substrate and positioned at a layer different from the trigger electrodes; and an address electrode provided at a lower substrate opposed to the upper substrate in a direction crossing the trigger electrodes.
In the plasma display panel, the trigger electrodes overlap with the sustaining electrode pair by a desired portion.
The plasma display panel further includes a first dielectric layer formed between the trigger electrodes and the sustaining electrode pair in such a manner to cover the trigger electrodes; a second dielectric layer covering the sustaining electrode pair and the first dielectric layer; and a protective film covering the second dielectric layer.
The plasma display panel further includes a floating electrode provided between the trigger electrodes.
A plasma display panel according to another embodiment of the present invention includes first and second sustaining electrodes provided at an upper substrate; first and second trigger electrodes provided between the first and second sustaining electrodes; a dielectric layer covering the first and second sustaining electrodes and the first and second trigger electrodes; and at least one shielding wall protruded from the dielectric layer.
In the plasma display panel, said shielding wall consists of two shielding walls protruded from the dielectric layer. Herein, said two shielding walls consist of a first shielding wall positioned between the first sustaining electrode and the first trigger electrode, and a second shielding wall positioned between the second sustaining electrode and the second trigger electrode.
In the plasma display panel, the shielding wall is protruded by more than 10 xcexcm from the dielectric layer. The shielding wall is made from the same material as the dielectric layer.
The plasma display panel further includes a protective film covering the dielectric layer and the shielding wall.
The plasma display panel further includes a floating electrode provided between the first and second trigger electrodes.
A plasma display panel according to still another embodiment of the present invention first and second sustaining electrodes provided at an upper substrate; first and second trigger electrodes provided between the first and second sustaining electrodes; and a floating electrode provided between the first and second trigger electrodes.
In the plasma display panel, the floating electrode has a width smaller than the first and second trigger electrodes. The floating electrode has preferably a width less than ⅔ of the widths of the first and second trigger electrodes.
In the plasma display panel, a voltage induced to the floating electrode is determined depending on voltages applied to the first and second trigger electrodes.